<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <button>点击我发送post请求的ajax</button>
    <script>
      let btn = document.querySelector("button");
      btn.onclick = function () {
        let xhr = new XMLHttpRequest();
        xhr.open("post", "/postdata");
        //   设置请求头部,表单格式
        // xhr.setRequestHeader(
        //   "content-type",
        //   "application/x-www-form-urlencoded"
        // );

        //   设置请求头部,json格式
        xhr.setRequestHeader("content-type", "application/json");
        //   发送的数据放到请求体里面
        // xhr.send("myname=zhangsan&age=20");
        xhr.send(JSON.stringify({ myname: "zhangsan", age: 20 }));
        xhr.onload = function () {
          if (xhr.status >= 200 && xhr.status < 300) {
            console.log(xhr.responseText);
          }
        };
      };
    </script>
  </body>
</html>
